Penicillins: Uses & Side effects

Penicillins are a type of antibiotic derived from Penicillium fungi. An antibiotic is a type of medicine that inhibits the growth of, or kills, bacteria.

Penicillin G (also called benzylpenicillin) was discovered by accident in 1928. Alexander Fleming, a Scottish physician-scientist was growing a type of bacteria called Staphylococcus Aureus on an uncovered petri dish when it became contaminated with mold spores. He observed that the areas of bacteria near the mold were dying. He isolated the substance from the mold that was killing the bacteria and called it penicillin.

Another naturally occurring penicillin, penicillin V was later isolated from the same mold. All other penicillins are semi-synthetic (made by modifying the structure of the original naturally occurring penicillins). Modification extends their spectrum of activity, allows them to be taken orally, and increases their resistance against penicillinase, an enzyme produced by some bacteria that inactivates penicillin.

Penicillins work by preventing the cross linking of amino acid chains in the bacterial cell wall. This does not affect pre-existing bacteria, but newly produced bacterial cells have weak cell walls that easily rupture.

What are penicillins used for?

Penicillins may be used to treat a wide range of infections caused by susceptible bacteria, such as:

  • Dental abscess
  • Ear infections (eg, otitis media)
  • Gonorrhea
  • Pneumonia
  • Respiratory tract infections
  • Rheumatic fever
  • Scarlet fever
  • Skin infections
  • Urinary tract infections.

Side effects

Penicillins generally cause few side effects. The most common side effects reported include abdominal pain, headache, rash, diarrhea, and taste perversion.

Penicillins may cause anaphylaxis in those allergic to penicillin, but the overall incidence of anaphylaxis is rare (0.01-0.05%).

Rarely, some people may develop a super-infection due to overgrowth of a naturally occurring bacterium called Clostridium difficile, following use of any antibiotic, including penicillins. Symptoms may include severe diarrhea.

Uncommonly, an overgrowth of the yeast, Candida albicans, may occur following penicillin use, resulting in the symptoms of thrush.


Keywords: Penicillins

* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.